Vehicle-grounding clamp

ABSTRACT

A grounding clamp is constructed of two arms pivotally interconnected intermediate the ends thereof with each arm having a handle end and a jaw end. The jaw ends of the arms are spring biased toward one another. The arms of the clamp are formed of a synthetic plastic having high electrical insulating characteristics. Replaceable metal jaw elements are secured to the jaw ends of the arms and the jaw elements include perpendicularly projecting spiked teeth. The teeth of each jaw element project toward the opposite jaw element, and the tips of the teeth of each jaw element lie in substantially parallel planes. An electrical lead extends to each jaw element with one of the leads grounded and the other lead in series circuit with a signal triggering device. When the clamp engages a portion of the vehicle to be grounded between the teeth, the vehicle is grounded and the triggering circuit completed through the vehicle. In an alternate embodiment, the teeth are formed by the pointed ends of mounting bolts which extend from the jaw ends of the arms through the jaw elements. A snap apart electrical connector is provided in an electrical lead cable which extends between an electrostatic drain and the clamp and the connector will open to prevent damage of the grounding clamp if the vehicle is moved without first removing the clamp.

United States pateiet Attaway [451 Feb. 8, 1972 [54] VEHICLE-GROUNDINGCLAMP [72] Inventor: Thomas J. Attaway, 50 SE. 14th St.,

Dania, Fla. 33304 22 Filed: May 28,1910

211 Appl.No.: 41,249

[52] US. Cl. ....339/14 R, 339/255 P [5 1] Int. Cl ..H0llr 11/22 [58]fieldofsearch ..339/14,255,260,59,28, 29;

2,522,810 9/1950 Bailey... ..339/200 3,470,523 9/1969 Milo ..339/451,910,022 5/1933 Legg 339/259 x 2,375,656 5/1945 Jackson ..339/255 P x119 25 957 2/1966 Caldwell ..317/2 R Primary Examiner-Marvin A. ChampionAssistant ExaminerRobert A. Hafer Attomey-Polachek & Saulsbury [57]ABSTRACT A grounding clamp is constructed of two arms pivotallyinterconnected intermediate the ends thereof with each arm having ahandle end and a jaw end. The jaw ends of the arms are spring biasedtoward one another. The arms of the clamp are formed of a syntheticplastic having high electrical insulating characteristics. Replaceablemetal jaw elements are secured to the jaw ends of the arms and the jawelements include perpendicularly projecting spiked teeth. The teeth ofeach jaw element project toward the opposite jaw element, and the tipsof the teeth of each jaw element lie in substantially parallel planes.An electrical lead extends to each jaw element with one of the leadsgrounded and the other lead in series circuit with a signal triggeringdevice. When the clamp engages a portion of the vehicle to be groundedbetween the teeth, the vehicle is grounded and the triggering circuitcompleted through the vehicle. In an alternate embodiment, the teeth areformed by the pointed ends of mounting bolts which extend from the jawends of the arms through the jaw elements. A snap apart electricalconnector is provided in an electrical lead cable which extends betweenan electrostatic drain and the clamp 7 Claims, 10 Drawing FiguresPATENTEWEB 81972 3.641.473

1 LIIK 1 INVENTOR THOMAS J. ATTAWAY BY W37? ATTORNEYS mmrm am SHEET 2 OF2 INVENTOR THOMAS J. ATTAWAY ATTORNEYS An electrical clamp having aseparate contact terminal in each jaw thereof.

During the loading and unloading of tank vehicles containing flammablefluids, there is a great fire and explosion hazard which is, to someextent, reduced by the provision of an electrical ground connected tothe vehicle. The electrical ground serves to discharge any electrostaticcharge which is carried by the tank vehicle. If the electrostatic chargeis not dissipated prior to the loading and unloading procedure, adischarge spark which might occur during the procedure could result inan explosion. The vehicle ground should be maintained during the vehicleloading and unloading operation because an electrostatic charge can alsobe accumulated by the movement of the flammable fluids in the tank.Thus, any charges must be continuously drained to a ground.

Several electrostatic drain devices have been developed to insure thatthe tank vehicle is continuously grounded during the loading orunloading operation. Most of these devices include not only a visible oraudible ground signal indicator but a switching mechanism which controlsthe operation of the pumping facilities so that the vehicle cannot beloaded or unloaded if a proper ground is not maintained. Generally theelectrostatic drain devices include a triggering circuit to activate theground signal indicator along with any auxiliary switching means tocontrol the fluid pumping operations. The triggering circuit includes agrounded terminal and the circuit is completed when a second terminal isadditionally grounded. A clamp serves to complete a series electricalcircuit between the grounded terminal and the second terminal throughtwo leads of a ground cable. Each lead of the ground cable iselectrically connected to one jaw of a ground clamp. Thus, thetriggering circuit is completed only when the tank vehicle is groundedthrough the ground clamp with the vehicle shunting between the twocircuit terminals.

Present ground clamps are constructed of electrically conducting metalarms which are pivotally interconnected. Because the ground clamp jawseach include terminals which must necessarily be insulated from oneanother and the metal arms, the jaws of the present ground clamps aremounted to the arms on insulated mounting pads with the securing means,e.g., bolts extending between the arms and the jaws,- further insulatedwith bushings. Due to the necessity of the insulating mounting padsalong with the insulating bushings to assure that the jaw terminals willnot short through the metal body of the clamp, the cost of the presentclamps are high. Furthermore, replacement labor costs for the individualjaw members are high because of the pad and bushing assembly process.Unfortunately, the jaw members often break. Breakage of the jaw membersis due to the fact that the tank vehicle often includes rusted orpainted surfaces which must be penetrated by the jaw member toadequately ground the vehicle. Thus, the jaw member teeth are subjectedto stresses, and breakage of individual teeth is common.

It is an object of the premnt invention to provide a vehiclegroundingclamp which is so constructed that it is not subject to any of theforegoing disadvantages.

More specifically, it is an object of the present invention to provide avehicle-grounding clamp which greatly reduces the explosion hazardinherent with the loading of flammable fluids in a tank vehicle, is easyto use, durable and sturdy in construction, yet can be fabricated bymass production techniques at a cost appreciably lower than vehiclegrounding clamps presently used.

Another object of the present invention is to provide avehiole-grounding clamp which is constructed of a body formed of asynthetic plastic and having replaceable metallic jaw elements which areelectrically isolated from one another.

A still further object of the present invention is to provide avehicle-grounding clamp which includes an electrically insulating bodyand replaceable metallic jaw elements each of which includes a pluralityof projecting teeth to engage portions of the vehicle to be grounded.

Yet another object of the present invention is to provide avehicle-grounding clamp which includes means to adjust the height ofclamp jaw teeth so that the tips of the teeth of opposed jaws lie insubstantially parallel planes to assure maximum electrical contactbetween the jaw teeth and the vehicle to be grounded.

Another object of the present invention is to provide avehicle-grounding clamp which includes an electrically insulating bodyand replaceable jaw elements with the jaw elements including teeth whichare formed by mounting bolts which hold the jaw plate to the body.

A still further object of the present invention is to provide avehicle-grounding clamp wherein the teeth of opposed jaws are formed bythe tips of mounting bolts which secure an electrical contact plate tothe clamp.

Other objects of the invention in part will be obvious and in part willbe pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements and arrangements of parts which will beexemplified in the vehicle grounding clamp hereinafter described and thescope of which will be indicated in the appended claims.

In the accompanying drawings, in which are shown the preferredembodiments of the invention,

FIG. 1 is a perspective view of -a vehicle-grounding clamp and showingthe clamp engaging a relatively flat metal portion of tank vehicleduring a tank-loading operation.

FIG. 2 is a side view of the vehicle-grounding clamp and showing jawteeth engaging a flat metal portion of the vehicle to be grounded; alsoshown is a snap apart electrical connector which is included in a twinlead electric cable running from an electrostatic drain device to theclamp.

FIG. 3 is a top plan view of the clamp illustrated in FIG. 2.

FIG. 4 is a sectional view taken substantially along the line 4-4 ofFIG. 2 and showing a cylindrical metal sleeve which is bent to engagethe twin lead cable running and thus prevent the cable from being pulledfrom the clamp.

FIG. 5 is a sectional view through the clamp the same being takensubstantially along the line 5-5 of FIG. 2 and showing a pin whichpivotally interconnects arms which form the clamp, along with a helicalcoil spring concentrically positioned about the pin and biasing the armsof the clamp so that the clamp jaws are urged together. 4

FIG. 6 is a sectional view through the jaw end of the clamp, the samebeing taken substantially along the line 66 of FIG. 2 and showingtoothed jaw elements seated within the hollow channel shaped portion ofthe clamp and secured therein by mounting bolts; additionally shown arejaw teeth which project from each jaw element toward the oppositeelement along with positioning shims interposed between the jaw elementsand the base of the channel shaped portion of the clamp.

FIG. 7 is a perspective view of the opposed jaw elements removed fromthe clamp and showing electrical leads extending to each jaw element.

FIG. 8 is a sectional view through an alternate embodiment of the clampwherein the jaw elements are constructed of contact plates and spikedjaw teeth are formed by pointed tips of bolts which secure the contactplate to the jaw end of the clamp.

FIG. 9 is an enlarged sectional view through the snapapart connectorelement, the same being taken substantially along the line 99 of FIG. 2.

FIG. 10 is a view similar to FIG. 7 but showing a still further modifiedform of the invention.

The vehicle-grounding clamp of the present invention to be describedhereinafter is designed for use in conjunction with an electrostaticdrain apparatus generally of the type illus trated in US. Letters Pat.No. 3,343,154 and U.S. Letters Pat. No. Re. 25,957 along with other,electrostatic drains which include a vehicle ground signal indicatorcontrolled by a triggering circuit in series with the vehicle to begrounded and an earth ground.

Referring now in detail to the drawings, the reference numeral denotes avehicle-grounding clamp constructed in accordance with an embodying theinvention. The grounding clamp 10 is formed of an upper and a lowerclamp arm 12, 14. Each arm l2, 14 is of substantially U-channeltransverse cross section as illustrated in the sectional view of FIG. 5.The arms include handle portions 16, 18 adjacent one end thereof and jawportions N, 22 adjacent the opposite ends thereof. The arms 12,114arepivotally interconnected by a pin 24 which extends through flangesprojecting in opposite directions from each arm toward the opposite arm.The pin,-in fact, extends through openings in the opposed flanges, andit will be noted, that the flanges which project upwardly from the lowerarm 14 are spaced apart a distance greater than the flanges whichproject from the upper. arm 12 and the flanges of the upper arm arenestably received between the lower arm flanges. The opposite ends ofthe pin 24 are suitably peened for captive retention. It will beobserved that when the handle portions 16, 18

of the arms are pivoted toward one another, the jaw portions 20, willseparate from one another.

It is desirable to have the jaw portions biased toward one another andelectrically engaging a metal portion of the tank vehicle. For thispurpose a helical coiled spring 26 is concentrically mounted about thepin 24 with the opposite end portions 28, 30 of the spring 26 extendingtangentially of the helical coils toward the handle portions, 16, 18.The spring end portions 28, 30 engage the hollow channel-shaped interiorof the arms l2, 14. Thus, a counterclockwise torque (as viewed in FIG;2) is applied by the spring 26 to the arm 12.

In order to increase the strength of the arms 12, 14 in the region wherethe spring ends 28, 30 apply forces against the arms l2, 14, each arm isprovided with a rib 32, 34 which projects in opposite directions fromthe arms l2, 14 respectively. The reinforcing ribs 32, 34 project fromthe bases of the proposed U-channel arms in opposite directions.

It should also be noted that the lower arm 14 includes a plurality, ofspaced parallel transverse grooves which provide finger grips in thehandle portion 18. Thus, the manipulation of the clamp is greatlyfacilitated and the user may quite readily grasp the handle portionswith his fingers seated in the grooves and squeeze the handle portionstogether against the bias of the spring 26 to spread the jaws apart,whereby a metal portion of the tank vehicle, may be received between thejaws and electrical contact will be achieved between the vehicle and theelectrostatic drain device.

Removable jaw members 38, 40 are seated within the U- channel interiorof the jaw portions 20, 22 of the clamp 10. The jaw members 38, 40include a substantially rectangular baseplate 42, 44 and a plurality ofspiked or pointed cylindrical protuberances 42 which projectperpendicularly from the baseplate 44. Each of the protuberances 46includes a pointed tip which serves to dig into a metallic surface ofthe vehicle to be grounded to assure an electrical contact. The jawmembers 38, 40 are preferably formed of molded one-piece construction.The width of the baseplates 42, 44 is less than the distance between thesidewalls of the U-shaped channel interior of the arms 12, 14 so thatthe jaw members may be inserted between the sidewalls of the arms andmounted therein with the longitudinal axis of the jaw members and thelongitudinal axis of the arms lying in substantially coplanarrelationship. In order to mount the jaw members 38, 40, threadedopenings 48 are provided through the baseplates 42, 44 and matinglythreaded bolts 50 extend through registered openings in the base of theU-channel arm to engage the threaded openings 48 It should be noted thatthe length of the spiked cylindrical protuberances 46 are uniform andthat the jaw portions 20, 22 of the arms l2, 14 do not move in parallelrelationship to one another when the clamp is opened and closed.Ideally, the metal surface of the tank vehicle which is to be groundedincludes two parallel flat surfaces and it is desirable therefore tomaintain the tips of the protuberances 46 of the jaw members 38, 40 insubstantially parallel relationship so that they the desired parallelorientation of the tips of the jaw members 38, 40. From an observationof FIG. 6 it will also be seen that the protuberances 46 projectingdownwardly from the baseplate 42 are displaced from the protuberances 46projecting upwardly from the baseplate 44. In fact, the embodiment shownincludes six protuberances 46 extending upwardly from the baseplate 44,and three protuberances extending downwardly from the baseplate 42. Itshould also be noted that the protuberances projecting downwardly liealong the longitudinal axis of the baseplate 42, while the protuberancesprojecting upwardly from the baseplate 44 are grouped in pairs, eachpair extending through a transverse plane perpendicular to the baseplate44. The transverse plane substantially includes the correspondingprotuberance projecting downwardly from the baseplate 42. Thus, the jawmembers 38, 40 include groups of three protuberances, i.e., two upwardlyprojecting and one downwardly projecting, with each group lying in atransverse vertical plane, and spaced from other groups of protuberanceslying in similar transverse planes. This specific protuberanceconfiguration permits three-point contact with each set (or group ofthree) protuberances extending in a single transverse plane. Thisthree-point contact will facilitate the gripping of curved surfaces bythe jaw members.

Attention is now directed to a twin lead cable 54 which extends into thearm 14 of the clamp 10. The cable 54 is sheathed in configuration. Thecable extends into the hollow U-channel interior of the arm 14 and iscaptively retained by a sleeve member 56 (see FIG. 4). The sleeve member56 is formed of a suitable bendable metal and tightly grips the cable54. It should also be noted that the sleeve member 56 is in turn securedto the arm 14 by a rivet 58 or the sleeve member may be made integralwith the arm 14 and form a tubing for the cable 54. The cable 54includes two leads 60, 62 which extend and, are electricallyinterconnected to the jaw members 38, 40 respectively. In order to makea secure electrical connection between the jaw members and theirrespective leads, each jaw member includes a flange 64 which projectsfrom the baseplates 42, 44 in a direction parallel to the protuberances46, but is' of a length less than that of the protuberances 46. Eachlead 60, 62 extends through an opening in a flange 64 and is then bentupwardly and secured under the head of a bolt 66.

It should be noted that an important feature of this invention is thefact that the jaw members 38, 40 are not electrically interconnectedthrough the clamp 10 itself and the only electrical connection betweenthe jaw members must be through a metal portion of the tank vehicle tobe grounded. To insure that the jaw members 38, 40 do not makeinadvertent electrical contact except through the desired vehiclemedium, this invention provides for an electrically insulating clampbody. For this purpose, the upper and lower arms l2, 14 are formed of asynthetic plastic which has a relatively high volume resistivity.Suitable synthetic plastics for use as the arms 12, 14 areacrylonitrile-butadiene-styrene, polypropylene, linear polyethylene(high density) and polystyrene. As previously mentioned, these syntheticplastics are highly suitable for upper and lower arm fabrication, andmay be easily injection molded. Additionally, their resistivity in ohmsper cubic centimeter is relatively high (approximately 10").Additionally, a suitable synthetic material for upper and lower armfabrication is glass reinforced polyester resin which is molded, and hasa volume resistivity in ohms per cubic centimeter of approximately 10'.

One should additionally note that in order to prevent electrical contactbetween the jaw members 38, 40 when the clamp is idle and there is nometal portion to be grounded between the clamp jaws, a suitable idleposition stop is provided. The stop is formed of rnatingly projectingbosses 64, 66 which abut one another before the spiked tips of theprotuberances 46 make contact with one another. Furthermore because theprotuberances 46 of each baseplate42, 44 are spaced from one another,the tendency for the jaw members 38, 40 to make electrical contactwithout an intervening metallic body is greatly reduced.

It should also be noted in passing that the jaw ends of the arms 12, 14include an upwardly projecting flange 68, 70 which serves as aprotective guard preventing damage to the bolt heads 50. This is becausethe flanges 68, 70 project from the base of the arms l2, 14 a distancegreater than the height of the bolt heads 50.

In order to prevent injury to the electrostatic grounding device and/orthe clamp or cable 54 if the tank vehicle is inadvertently moved,without first disconnecting the grounding clamp 10, a pull apartelectrical connector 72 is provided in the cable 54. The connector 72includes two snapapart sections 74, 76, each of which includes alongitudinal socket 78 which receives a mating cylindrical contact plate80 which projects from the opposite section. If the vehicle is movedwithout first disconnecting the grounding clamp 10 the section 74, 76will separate, and the respective contact plates 80 will slide from thesockets 78. Thus, the vehicle will move with the grounding clamp 10attached along with a portion of the cable 54 leading to and includingthe connector section 76.

An alternate embodiment of the invention is illustrated in the sectionalview of FIG. 8. In this embodiment the upper and lower arms 12a and 140include jaw members 38a and 400 which are of a difi'erent configuration.The jaw members 38a and 40a include rectangular baseplates 42a and 44awhich are nestably received within the hollow U-channels of the jawportions a, 22a of the arms. The baseplates 42a, 44a do not includeone-piece unitarily formed protuberances, however, and in facttheprotuberances are formed by the bolts 500, which secure the baseplate44a to'the base of the U-channel of the arm 14a. The baseplate 44aincludes a plurality of threaded openings 48a which are positioned anddistributed along the surface of the baseplate in the same pattern ofthe protuberances 46 of the preferred embodiment. The bolts 50a are of alength longer than the length of the previously used bolt 50 (in thepreferred embodiment and include spiked or pointed tips. In order tomaintain the tips of the bolts 50a in proper planar alignment and toinsure that the tips of the bolts 50a of 'both jaw members lie insubstantially parallel planes, each bolt is individually adjustablethrough the use of shim washers78. The baseplates 42a, 440 are securedto the jaw portions 20, 22 of the arms by the bolts 50a which extendthrough openings in the jaw portions 20a, 2741 in registry with thethreaded openings 48a of the baseplate.

As was previously mentioned, the distance which the tips of the bolts50a extend past the baseplate is adjustable through the use of washershims 78. Thus, in the application illustrated in FlG.'8 the bolt whichis adjacent the boss 640 should extend a distance beyond the baseplate444 which is greater than that of the other bolts. Therefore this boltdoes not include a shim washer 78. The precise adjustment of the bolt isin fact determined by the specific vehicle application and therefore isnot of critical importance. It should also be noted that the baseplates42a, 440 are connected electrically to their electrical leads 60, 62through the use of the bosses 64a and 66a in a manner identical to thatof the preferred embodiment.

A further embodiment of the invention is illustrated in FIG. 10. In thisembodiment, a clamp 10b is identical in construc' tion to the clamp 10previously described except for a slight variation in the jaw members38b, 40b.

This embodiment employs an alternate structure for securing electricalconnections between the jaw members 38b, 40b and their respective leadsb, 62b. Each jaw member includes a bore 80 in the rear wall of itsbaseplate 42b, 44b which accommodatingly receives the stripped terminalend portion of the leads 60b, 62b respectively. The bores 80 extendinwardly along the longitudinal axis of each baseplate.

A setscrew 82, extending in a tapped transversepassageway running from asidewall of the baseplates to the bore'80 bears against the end portionsof the leads totightly engage" the leads.

A further feature of the invention is the fact that the jaw members 38,40 may be easily replaced if the spike tips of the protuberances 46become damaged. In fact, one advantage of the present invention is thatbecause the clamp arms are constructed of a synthetic plastic which'hasdesirable insulating characteristics, there is no need to provideinsulating washers and bushings to isolate the jaw members from the bodyof the clamp.

Thus it will be seen that there has been provided a vehiclegroundingclamp which fulfills the stringent safety'requirements of tank vehiclesloading operations and is easy to operate and maintain.

As various possible embodiments might be made of the present invention,and as various changes might be made in .the embodiments above setforth, it is to be understood that all matter herein described or shownin the accompanying drawings is to be interpreted as illustrative andnot in a limiting sense.

What is claimed is: V

l. A clamp for grounding flammable-liquid-transporting vehicles anddissipating any electrostatic charges carried by the vehicle, said clampcomprising a body, said body including two jaw portions, means formoving said portions relative to one another, means biasing the jawportions toward one another, a jaw contact member for each jaw portion,the jaw portions including means for receiving its associated jawcontact member, each jaw portion being constructed of one "piece moldedsynthetic plastic, electrical lead means, the electrical lead meansextending from an electrostatic drain device to each jaw contact memberwhereby a series electrical circuit may be completed from each leadthrough the respective jaw contact member and through an electricallyconducting portion of the vehicle body to drain any electrostatic charge'carried by the vehicle during a flammable-fluidloading opera tion,wherein the body is formed of two arms, means pivotally interconnectingthe arms intermediate the ends thereof, 'each arm including a handleportion adjacent one end thereof and on a common side of the meanspivotally interconnecting the arms, the jaw portions being formed ineach arm on theopposite side of the means pivotally interconnecting thearms, each arm being of one-piece molded synthetic plastic construction,wherein the means biasing the jaw portions toward one another includes ahelical coil spring, the means pivotally interconnecting the armsincludes a pin, the helical coil spring having convolutions which extendsubstantially concentrically about the pin, wherein each jaw contactmember includes a baseplate and a plurality of spiked protuberancesprojecting therefrom, means mounting the jaw contact members in themeans receiving the jaw contact members, the mounting means including aplurality of bolts, each of said bolts having a spiked tip, the boltshaving their longitudinal axis in substantially perpendicularrelationship to the base plate, the bolts extending from the jawportions through the baseplate and outwardly therefrom, the portion ofeach bolt extending outwardly from its respective baseplate forming thespiked protuberance, and the jaw contact members being formed of metalin a one-piece construction, whereby the spiked protuberances mayreadily engage an electrically conducting portion of the vehicle body.

2. A clamp constructed in accordance with claim 1 wherein means forminga plurality of parallel spaced grooves across one of the handle portionsin a direction transverse to the length thereof is provided, whereby themanual grasping of the handle portion is facilitated by the placement ofthe user's fingers within selected grooves.

3. A clamp constructed in accordance with claim 1 wherein the spikedprotuberances in one jaw contact member extends along the longitudinalaxis of the one contact member and the member, the spiked protuberancesof the other contact member being grouped in pairs with each pair lyingin a plane transverse to the longitudinal axis of the other contactmember base and an associated spiked protuberance of the one jaw contactmember lying in the same transverse plane whereby at least three-pointmechanical contact may be made between the respective jaw contactmembers over an electrically conductive curved surface of the vehicle.

4. A clamp constructed in accordance with claim 1 wherein shims areprovided, said shims being spaced between the baaeplate of each jawcontact member and the means receiving each' jaw contact member, wherebythe tips of the spiked protuberances of the respective jaw contactmembers may be positioned in substantially parallel relationship.

5. A clamp constructed in accordance with claim 1 wherein means foradjustably varying the length of each spiked protuberance is provided,said adjustment means comprising shim washers, said shim washers beingspaced between the heads of the bolts and the jaw portions to vary theeffective length of each bolt.

6. A clamp constructed in accordance with claim 1 wherein means isprovided for automatically disconnecting the electrical lead meansbetween the electrostatic drain device'and the I clamp if the vehicle isinadvertently moved while the clamp is still affixed to the vehicle,said automatic disconnecting means I comprising a snap apart electricalconnector, said electrical connector being positioned in the lead meansintermediate the clamp and the electrostatic drain device. I

7. A clamp constructed in accordance with claim 1 wherein coupling meansis provided to mechanically interconnect each jaw contact member and theelectrical lead means, the

1. A clamp for grounding flammable-liquid-transporting vehicles anddissipating any electrostatic charges carried by the vehicle, said clampcomprising a body, said body including two jaw portions, means formoving said portions relative to one another, means biasing the jawportions toward one another, a jaw contact member for each jaw portion,the jaw portions including means for receiving its associated jawcontact member, each jaw portion being constructed of one piece moldedsynthetic plastic, electrical lead means, the electrical lead meansextending from an electrostatic drain device to each jaw contact memberwhereby a series electrical circuit may be completed from each leadthrough the respective jaw contact member and through an electricallyconducting portion of the vehicle body to drain any electrostatic chargecarried by the vehicle during a flammablefluid-loading operation,wherein the body is formed of two arms, means pivotally interconnectingthe arms intermediate the ends thereof, each arm including a handleportion adjacent one end thereof and on a common side of the meanspivotally interconnecting the arms, the jaw portions being formed ineach arm on the opposite side of the means pivotally interconnecting thearms, each arm being of one-piece molded synthetic plastic construction,wherein the means biasing the jaw portions toward one another includes ahelical coil spring, the means pivotally interconnecting the armsincludes a pin, the helical coil spring having convolutions which extendsubstantially concentrically about the pin, wherein each jaw contactmember includes a baseplate and a plurality of spiked protuberancesprojecting therefrom, means mounting the jaw contact members in themeans receiving the jaw contact members, the mounting means including aplurality of bolts, each of said bolts having a spiked tip, the boltshaving their longitudinal axis in substantially perpendicularrelationship to the base plate, the bolts extending from the jawportions through the baseplate and outwardly therefrom, the portion ofeach bolt extending outwardly from its respective baseplate forming thespiked protuberance, and the jaw contact members being formed of metalin a one-piece construction, whereby the spiked protuberances mayreadily engage an electrically conducting portion of the vehicle body.2. A clamp constructed in accordance with claim 1 wherein means forminga plurality of parallel spaced grooves across one of the handle portionsin a direction transverse to the length thereof is provided, whereby themanual grasping of the handle portion is facilitated by the placement ofthe user''s fingers within selected grooves.
 3. A clamp constructed inaccordance with claim 1 wherein the spiked protuberances in one jawcontact member extends along the longitudinal axis of the one contactmember and the spiked protuberances of the other jaw contact member arespaced from the longitudinal axis of the other contact member, thespiked protuberances of the other contact member being grouped in pairswith each pair lying in a plane transverse to the longitudinal axis ofthe other contact member base and an associated spiked protuberance ofthe one jaw contact member lying in the same transverse plane whereby atleast three-point mechanical contact may be made between the respectivejaw contact members over an electrically conductive curved surface ofthe vehicle.
 4. A clamp constructed in accordance with claim 1 whereinsHims are provided, said shims being spaced between the baseplate ofeach jaw contact member and the means receiving each jaw contact member,whereby the tips of the spiked protuberances of the respective jawcontact members may be positioned in substantially parallelrelationship.
 5. A clamp constructed in accordance with claim 1 whereinmeans for adjustably varying the length of each spiked protuberance isprovided, said adjustment means comprising shim washers, said shimwashers being spaced between the heads of the bolts and the jaw portionsto vary the effective length of each bolt.
 6. A clamp constructed inaccordance with claim 1 wherein means is provided for automaticallydisconnecting the electrical lead means between the electrostatic draindevice and the clamp if the vehicle is inadvertently moved while theclamp is still affixed to the vehicle, said automatic disconnectingmeans comprising a snap apart electrical connector, said electricalconnector being positioned in the lead means intermediate the clamp andthe electrostatic drain device.
 7. A clamp constructed in accordancewith claim 1 wherein coupling means is provided to mechanicallyinterconnect each jaw contact member and the electrical lead means, thecoupling means including means forming a bore in each jaw contactmember, the electrical lead means including two electrical leads, anelectrical lead extending into each bore, the coupling means furtherincluding means forming a transverse passageway in each jaw contactmember, each of said passageways extending into its respective bore,each passageway including a setscrew, the setscrew bearing against theelectrical lead seated within the bore.